1. Field of the Invention
This invention relates to a carriage for guiding a tool along a specified path on a workpiece and, more particularly, relates to guiding a tool along a flange on a workpiece at a controlled, substantially constant speed.
2. Description of the Prior Art
In welding operations, the majority of jobs which require moving a tool along a specified path on a workpiece at a controlled speed are still mainly done manually with stick electrodes. However, an increasing number of such jobs are being automated. Machines that perform such automation usually include a tool attached to a drive car that travels on a track adjacent to the workpiece. This track has to be aligned and attached to either the workpiece or an adjacent fixture, taking up valuable production time.
Further, if the job requires cutting or welding along a path other than a straight line, such as along curves of varying radii, the track has to be made to conform to the contour of the workpiece. Forming such a track may be impractical, if not impossible. Furthermore, when the track is adjusted for use with a curved workpiece, the radius of curvature of the track may be different from the radius of curvature of the work path by an offset amount. This means that the drive speed of the tool guiding apparatus must change on the curved path as compared to the straight path to compensate for this difference and keep the speed of the tool substantially constant.
In the devices that use a guiding track conforming to the shape of the workpiece, the fabrication and setup of the guiding track must be precise, since any deviation will not be compensated for unless additional takeup mechanisms are provided. These takeup mechanisms, in turn, tend to make the apparatus unwieldy.
There are a few machines that do not use a track for guidance. These are mostly gravity-assisted friction devices that have lateral guide rollers to follow the work path, typically following a vertical flange member for a fillet weld joint. However, these devices are generally meant for straight line runs only and are large and heavy since they depend on gravity for stability.
Accordingly, it is an object of the present invention to overcome the deficiencies in the prior art with respect to guiding a tool along a specified path on a workpiece at a controlled, substantially constant speed.